Television system



Nov. 6, 1951 Q C, SZIKLA, 2,573,777

TELEVISION SYSTEM Filed April 24, 1947 INVENTOR.

wly film ATTORN EY' Patented Nov. 6, 1795-1 TELEVISION SYSTEM George C.Sziklai, Princeton, N. J., assignor to Radio Corporation of America, acorporation of Delaware Application April 24, 1947, serial No. 743,487

This invention relates to image reproducing systems and moreparticularly to reproduction in a simultaneous manner of a plurality ofcornponent images such as, for example, component color 4images toproduce a composite color image. As is well known in the television art,the transmission of visual information over electrical circuits such asa radio circuit can be accomplished by analyzing the image into itsimage elements and deriving therefrom a signal train of impulses -by anorderly sequence of scanning. The image may then be reproduced from theelectrical signal train by reconstruction in the same orderly sequenceof scanning. A multiple image transmission may be accomplished by'asequential or a simultaneous type of transmission. The sequential systemreferred to transmits one image or component image at a time in sequenceand at a rapidly recurring rate.

The simultaneous system transmits through three separate adjacent orcontinuous or even discontinuous and spaced signal channels all theimages Yor component images simultaneously. It has been know for manyyears that the transmission of television images in color may beaccomplished by transmitting signals representative of the image in eachof a selected number of primary or component colors, which are three innumber for a tricolor system or which may 1nclude, where desired, amonochrome signal addition known as the key image to sharpen imageoutline and delineation. For a low degree of fidelity of colorrepresentation, even a bicolor `system might be adopted.

For any of rthese methods, however, the several produced component colorsignal series may be transmitted simultaneously when a simultaneousmulticolor method is adopted, or they may be transmitted in sequencewhere a sequential additive method is adopted. For the purpose ofreference herein, the three selected component colors will be mentionedas red, green, and blue, although any suitable three colors maybeselected with the condition being that 1all are to add to produceavhite, and that no two shall add to produce the third color. Of course,the selection is best where the greatest portion of the I. C. I. colortriangle is usable.

YThe transmission of color images -by the well known sequential systeminherently leads to color action fringes and color flicker, unless thefield frequency is raised to a very high value which leads to arequirement for a very broad frequency band forsignal transmission. Y j-lt becomes apparent that the transmission and 11 claims. (ci.A17e-.5.4)

, 2 reproduction of lcomponent -color images simultaneously to produce acomposite image would eliminatethe disadvantages referred to above.

.There is, however, one important difliculty in the simultaneousreproduction of component images. It will be remembered that in anadditive process of color reproduction, it is essential that the severalcomponent color images must be in substantially perfect registry toproduce desirable results.

When three separate physical devices are employed, one for each of thecomponent colors, there maybe involved diiiiculties in making optical,electrical, and mechanical alignment ywhich preclude the 4convenientadjustment for pro-per registration of theseveral component images.

According to this invention, a system of image reproduction is `employedwhich alleviates the necessity yforrepeated adjustment of individualimage registry. An -image reproducing tube is provided wherein theseveral component color. images are projected in registry on a singlescreen of the tube.

- There have `been proposed heretofore several ingeniousgdevices foraccomplishing the reproduction of several component images on a singlescreen of an image reproducing tube. Such a device,forexample, has beenproposedwherein a screen ofan image producing tube is divided into alplurality of elemental areas undiscernible to Atheunaided eye butselectively characterized to generatea predetermined component color.Such asystem, however, is subject to difficulties ubecause of theproblems involved in deflection of the electron stream at high velocity.

It is well known inthe electronic art that a deflection of an electronbeamfmay be accomplished with greater ease and accuracy when theelectron beam is travelling ata relatively low velocity. vIn the colorsystem heretofore proposed wherein the electron beam is directedselectively to the proper, elemental areas of .the viewing screenginaccordance with the incoming componentucolor image signal train, thedeflection of the beam is accompanied by inaccuracies and otherdiiiculties by reason of the fact that, in order toproduce a suicientlybrilliant image, the electrons.A of-the beam must be travelling atarapid rate. K

According to thisinventon, it is not necessary to deflect the electronsafter they have been accelerated to a high rate to produce a brilliantimage. y The required deflection for purposes of forming a scanningraster is accomplished before theima'ge is. formed, vand after there isformed derived an electron image representative of the raster. Themodulation of the scanningfraster is then accomplished by modulating thevelectrn stream between the photo cathode and the lumi= nescent screenof the image tube.

According to this invention, the scanning raster erators 'I and 9 havebeen wellv described in theV the type shown and described in the U. S.patenti to A. V. Bedford, No. 2,207,775, dated July 16,

1940. The horizontal and deection signal gen- U. S. patent toY W. A.Tolson et al., No. 2,101,520,

Y dated December 7, 1937, or as in the above mentioned now marketedreceivers. The patents and.

apparatuslisted are given -by Way of lexample only. VAny suitabledevices for performing the same functions are satisfactory for employmenthe practice of ythis invention. Y

Video amplifier 3 must, ofcourse, be capable 'of transmitting a widefrequency band and may ftake any of the `welllknown forms,'such as, for

produces by electronic bombardment an electroni image of secondaryelectrons. The electron flow from the electron image to theassociatedluminescent screen is modulated by a video signal topr'oducewan intelligence image.

` `The transmission 'of stereoscopic images :can'b accomplished if theidentity of the rig-ht and left eye views can be maintained throughouttransmission. and reproduction. The identity can b'e maintained duringtransmission by sending right and left eye views. separately. Systemsvofthis type V'have been. proposed employing vertical opaque strips Ywhose'width and spacing vand distance from the image are chosen such that theimage, which is Vmade up of .alternate vertical strips representativeofalternatelyfright and left eye views, will'be resolved into astereoscopic image. v

This invention in one `of itspreferred forms lends itself vparticularlywell lto the reproduction of stereoscopic images. I

A primary object of this invention is therefore to .provide an 'improvedtelevision system.

Another object vof this invention is to .provide fl tion which is4substantially free from registration L dfculties. I

other andsncide'tal objects of the invention Y will be apparent to thoseskilledfin the'art #from a reading of the following specification andfan inspection of the 'accompanying l'i'.rafviing vin which Figure J2illustrates schematically-one 'preferred form of this invention'adaptableto-fthe simul taneous reproduction of component images such asis involved in the simultaneous reproduction of' coloiI images Figure 3shows Vgraphically the operation of the simultaneous type ofreproduction; `and Figure 4 illustrates another form which lthe image'reproducing' tube may take.

llurning now in detail to `Figure ,1, there is shown a televisionreceiver I, its associated video ampliiier 3, async separator 5,horizontal deflectionigenerator 1, and Vvertical deectionigenerator '9.y ments may take any of the well known forms such as, for example, thatshown in the vCa'rl's'on Reissue Patent No. 20,700, dated -April 19,i1-938, or, for instance, that `marketed `atpresent by the assigneecompany 'and known as Models `630TS and/or 621TS. A sync separator whichmaybe employed to separate the synchronizing signals from the videosignals may, Ifor example. :be of The yreceiverV andA the associatedel'el example, .the ltype shown and described in an Y article entitledCathode-Coupled .Wide-Band y f Ampliiiers -by GLC. Sziklai and A.,C.Schroeder, j. beginning on page V701 of ythe Proceedings of the,lnstiftute of Radio Engineers forOctober,

1945, or may be of the fform disclosed by U. S.

patent application fof J. C. Achenbach, S. I. Tour-Y shou, and I.Mackey, Serial No. 638,780,1iled January 3, 1946, also by way ofexample.

" Tube His provided for the purpose of estab.-Y

ode ray beam secondary emissive electrode element orcathode i1 byhorizontal deection coils I9 and deiiectionA coils 2i.

, The electron gunis ldiscussed' in detail in-an ,j article entitledFactors Governing Performance 1 t of Electron Guns in TelevisionCathode-Ray Tubes" byR. R. Law, beginning on page l0'3fof theProceedings of the-InstituteV of RadioEnjf-j gineersA for February,'1942, and invv an article entitled Improved Electron yGrun for.Cathode- Ray Tubes. by L. Swedlund in Electronics for March, 1945. l

.Deiiection coils `lt'and 2| may, 'for example,` take the Vformshownand-descrbed in the IJ. S. f patentto W. A. TolsomNo. 2,167,379,dated July j The vsecondary 'emissive 'electrode lll must Vbe ofadequate size to receive the scanningraster;r` and is provided Ywith astructure and madeof a i material capable of ,providing adjacent toitself? an'electron image of `the scanning raster-byseo-l vonclaryemitted electrons 'as a result .of the elcf tronic bombardment bythecathode ray beamiS.

trons from. the metallic surface. secondary emission.V

The velocity or' voltage vat which secondary electronsfareemitted-depends 'on Vthe' nature of the surface from Whiohthe eiectr'onsare emitted and the velocityof thebo'mbarding electrons will alsobe. 'acontrolling .factor indetermining the quantity offreleasedfsecondaryelectrons.

1t will beseemlthereiore, that the electron beam I5 W'ill produce atthe'pointf'of intersectionY with secondary emissive electrode I7avgroupoffsecondary `electrons which form an electron-image.

of the scanning raster.4

` IA device fcalled the'i-'mage tube has-been devel.-V

oped which will. convert an electron image Ii1-m; an'opticalimage."A x Al vertical c The operationof an image tube'has been'fout-g. 'Y lined 1in'detail Vbeginning on page 3,85 of the RCA Revie for September, 1946.The 'image'tub'e' and an electron lens system contained in an evacuatedglass envelope. When an image isfocused on its photo cathode, electronsare emitted from it with a density distribution which corresponds Ytothe distribution of illumination on the photo cathode. These electronsare accelerated and focused by an electron lens into an image whichimpinges upon the associated uorescent screen. Here the energy containedin the speed of the electrons is converted into visible light, thusreproducing the image focused on the photo cathode.

Thel electron lens system employed in the image tube is comparable inmany respects to an optical lens system. It consists of a series ofcoaxial cylinders with various potentials applied as indicated, forexample, in the image tube section of -tube Il shown in Figure 1 ascylinders 20.

Y, ,By controlling the flow' of electrons from the secondary emissiveelectrode to its associated `luminescent screen 23 with a video signal,an

image may be produced on the luminescent screen 23 from a blank scanningraster projected on the electrode Il, if the system is maintained insynchronism with the image pickup system. The image produced onluminescent screen 23'may be viewed directly or projected as illustratedto screen 25 through a lens system I28.

'Ijhe modulation of the electron flow from the secondary emissiveelectrode Il to the associated luminescent screen 23 is accomplished byproviding an electrode 21 maintained at a substantially constantpotential such as ground potential, as illustrated in Figure 1, incombination with avariable potential applied to secondary emissiveelectrode I1. The quantity of electrons passing from the secondaryemissive electrode I1 to the luminescent screen 23 will be governed bythe difference `in potential between the secondary emissive electrodeand the electrode 21. If. forexample, the potential of the secondaryemissivev electrode H is negative with respect to the potential of theelectrode 21, the electrons will be attracted away from the secondaryemissive electrode l1 and pass through the mesh of the electrode 2l tothe luminescent screen 23. If,

however, the potential ofthe secondary emissive electrode Il is positivewith respect to the potential of electrode 2l, the secondary electronswill be repelled by electrode 27.

It will be seen, therefore, that the transmitted television image may bereconstructed on the luminescent screen 23 by varying the potential ofthe secondary emissive electrode l1 in accordance with the video signalsobtained from video amplier 3.

In Figure 2, there is shown still another preferred form of thisinvention involving the image tube electron flow modulation principleexplained under Figure l above, however, the secondary emissiveelectrode 3| of tube 33 is so constructed that it contains a pluralityof miniature parallel elements, every third, one, for example, beingThere is also'contained in tube 33 and electrode 4| positioned betweenthe secondary emissive electrode 3| and a luminescent screen 43 andconnected to a substantially constant potential such as ground, asillustrated. The electron lens of tube 33 is provided by the elements45.

Green signal channel lil is connected to one set of` the elements of thesecondary emissive electrode 3|, blue signal channel de is connected toanother set of the elements of secondary emissive electrode 3|, and redsignal channel 5| is connected tothe third set of elements of electrode3|. Y

It follows from the explanation of the operation of tube in Figure lthat when, for example, a negative signal is s-upplied to the elementsof the secondary emissive electrode 3| connected to the green signalchannel, and a positive potential is applied to the other elementsconnected to the blue signal channel 43 and the red signal channel 5|,electrons will flow to the luminescent screen i3 only from that portionof the electron image formed by and adjacent the secondary emissiveelectrode 3|, which is at a negative potential with respect to thecontrol electrode 4| or the elements of the secondary emissive electrode3| which are connected to the green signal channel 4l.

There will, therefore, be projected on the luminescent screen 63 aseries of vertical lines representative of the electron image adjacentthe elements of secondary emissive electrode 3|, which are connected tothe green signal channel 41.

f If, however, theincoming signal changes such that the blue signalchannel i9 produces a negative signal with respect to the controlelectrode 13| and at thesame time the green signal channel l and the redsignal'channel 5| both produce a signal positive with respect to thepotential of the control electrode 4|, a series of minute vertical lineswill be produced on screen d3 which correspond in position to theelements of secondary emissive electrode 3| which are connected to theblue signal channel 59. f

It follows that, if the luminescent screen 133 is composed of colorproducing phosphors or component color llters whose position and widthcorrespond to the electron image produced adjacent the secondaryemissive electrode 3l, and whos-e colors correspond to the associatedsignal channels, a composite color image may be reproduced on theluminescent screen 43.

It often becomes desirable to control the intensity of the electron beamproducing the scanning raster on secondary emissive electrode 3|. Thisis accomplished by applying a signal to control electrode 53 throughbeam intensity control channel 55. The intensity of the beam may becontrolled for purposes of blanking, or for purposes of supplementingthe color image with a black and White image either ofy the same ordifferent than that transmitted through the channel controlling theelectron flow through the image tube.

Very often in practice the green signal channel 41 is employed for thetransmission of synchronizing and blanking signals. This may beaccomplished by connectingbeam signal control channel 55 with the greensignal channel 41.

TheA operation of the secondary emissive electrode or electron imageforming device may be further explained by reference to Figure 3.

Blocks 6| represent in greatly enlarged cross section 4the elements ofthe secondary emissive electrode 3i of Figure .2. Everylthird one of theblocks 6l is interconnected to each other to form, for example, a redsystem, a green system, and a blue system, as illustrated. A controlelectrode $3 is positioned adjacent the elements 6I and connected toground.

. 1f, for example, a negativesignal with respect to ground is connectedto Athe .red elements, the electrons emitted from the elements will passthrough the screen structure of the control electrode 63 on to theluminescent screen 65, as illustrated by the arrows. applied to thegreen and blue elements as illustrated, the electrons emitted from thegreen and blueelements 6i lwill .be repulsed and prevented from passingthrough the vcontrol electrode 63 to the luminescent screen 65. asillustrated by the curved arrows.

It follows that, if screen65 is composed, as illustrated, of colorproducing phosphore or component color lters whose width corresponds .tothe width of the electron image of the elements BI of the secondaryemissive element .and whose colors correspond to the associated signalchannels, a color image may be reproduced'on luminescent screen 65.

In Figure 4, there is shown still another preferred form of thisinvention wherein the .elecf tron gun structure 1l directs an electron.beam at a secondary emissive electrode 13. The electron beam may bedeilected, for example, by deflecting plates 15. The intensity of theelectron beam may be controlled by control electrode 11.

An electrode 19 is `positioned adjacent the secondary emissive electrode13 and -is connected to a video signal channel 8|. There is provided aluminescent screen 83which is adapted to re produce optically theelectron .image 'formed .adjacent the secondary emissive electrode 13 byreason of the electron .lens system involving .elecbe made elliptical byproper beam focusing arrangement, the narrow dimensionbeing in v:tlfiedirection of the line or rapid scanning .motion Having thus describedthe invention, -what'is claimed is:

1. An image reproducing device comprising combination an electrode to.emit .electrons vfrom elemental Yareas thereof by secondary emission,said electrode having separate selective and termingled groups ofinterpositioned, .electrically interconnected and electricallyconductive elemental areas extending across substantially rall the areaof said electrode, anzelectron lens system positioned in ythe path oiVsaid electrons, a luminescent screen having separate and inten mingledgroups of irrterpoeitioned elemental areas covering substantially allthe area :of said luminescent screen, and whose elemental .areas are insubstantial .registry with `the electron image of the..correspondingelemental .areas of said electrode, a conductive gridpos'itioned--between said electrode and said screen, ysaid gr-i'd connected to apoint of fixed potential, means for developing a scanning rasteron saidelectrode, and means connected ltovsaidlielectrodeto If a positivepotential vis i8 cont-rolthe' magnitude or flow "of electronsin.-dependently from eachgroup of Velemental .areas of. said electrode tothe corresponding group of elemental areas of said'luminescent screen.2. A `color image :reproducing device comprising in combinationelectrode means to emitelec'- trons. upon electronic bombardment, said.electrode means .consisting Yof separate component colorrepresentativeV and intermingled groups' of sequentiallyinterpositioned, electrically inter.- connectedandelectricallyconductive'strip shaped electrode means, a ruled luminescent screencon-` sisting lof separate groups of strips, each group consisting vofdifferent" colors and being Vin subr` stantial registry with theelectronimage ofthe corresponding krepresentative color group of 'saidelectrode means, means for developing a scanning rasterV on Vsaidelectrode means,'means to control Y the magnitude -of the now ofelectrons y'fronreach group of elemental `areas of said electrode meansto the corresponding group of elemental areas ofv said luminescentscreen, and meansr connected to said'electron 4low magnitude controlymeans to Y vary the potential applied thereto to construct an Yintelligence image 4on saidduminescent"screen.

3. `A color imageyreproducingdevice compris#V ing in combination meansto emit electrons from .elemental areasV only upon'electronic *bomba-rd#ment' of said elemental areas and having associated therewith yseparatecomponent 'color j representative and intermingled groups of se-`Vquentially in-terpositioned, electrically `'intercona nected andelectrically conductive strip shapedV elemental areas extending acrosssi-ibstant iallyV all the area -of 'said electronVv emissive means, anelectron "lensjsystem'V positioned the path of said electrons; VaYsubstantially jwhi-te light 'pro-fVV ducing luminescent screen, and aruled color lter associated therewith the consisting of strips of ing-ascanning 'raster o'nsaid electron emisssive means, Ameans to control the4 magnitude of the ow of electrons'from each group of elemental areas ofsaid electron emissive means to the correspondir-xgvr groupV ofelementalf areas of saidV f intelligence image on saidluminescentscreen:

tem, a luminescent screen, said Velectrollllerl S sys?4 temV positionedbetween .said secondary emissive element andfsaid luminescent screen,means for.

bombarding said secondary .electron .emissive Vele'- ment with an'electron beam .to forma blank scanning raster on said element, anelectrode positioned between said secondary kelectron omis-V Y siveelement and -said luminescent screen .to ycontrol the magnitude of 7theflow of electrons from saidv secondary electron emissive element to.said

luminescent screen upon a Achange inthe po# tential of said electrodewith respect'to .the Ipo-. 'Y

ment to v ary the potential therebetween ltoconstruct an intelligenceimage on said luminescent screen.

5. In a television system, an image reproducing device comprising incombination an element to produce electrons by secondary emission uponelectronic bombardment, an electron lens system positioned in said imagereproducing device, a luminescent screen, means for developing a blankscanning raster on said cathode, a control electrode positioned betweensaid cathode and said luminescent screen to control the magnitude of theflow of electrons from said cathode to said luminescent screen upon achange in control electrode potential relative to the lpotential of saidcathode, and means connected to said control electrode to vary thepotential applied thereto.

6. In a television system, an image reproducing device comprising incombination a secondary electron emissive cathode, an electron lenssystem positioned adjacent said secondary electron emissive cathode, aluminescent screen, means for developing an electron image of a blankscanning raster adjacent said cathode, a control electrode positionedbetween said cathode and said luminescent screen, means for maintainingsaid control electrode at substantiallyr a constant potential, and meansconnected to said cathode to vary the average potential of said '7. In atelevision system, an image reproduc- :1f

ing device comprising in combination a secondary emissive cathode, anelectron lens system, a luminescent screen, said electron lenspositioned between said cathode and screen, means for developing a blankscanning raster in the form of an electron image adjacent said cathode,a control electrode positioned between said cathode and said luminescentscreen, means for maintaining said control electrode at a predeterminedpotential, said cathode having 'as a part thereof a plurality oi"separate electrically insulated elemental areas, each to control themagnitude of the ow of electrons from said cathode to said luminescentscreen, and means connected to each of said elemental areas of saidcathode to vary the potential applied thereto to construct anintelligence image on said luminescent screen.

8. In a television system, an image reproducing device comprising incombination a secondary emissive element comprising a plurality ofseparate electrically conductive electrodes, an electron lens systemcooperatively positioned with said secondary emissive element, aluminescent screen, means for developing a blank scanning raster on saidcathode, a control electrode positioned between said cathode and saidluminescent screen, separate control means connected to each of saidelectrodes of said cathode and means for applying a component signalrepresentative of a portion of an intelligence image to said controlmeans to vary the potential applied to said electrodes to control incombination with said control electrode the magnitude of the flow ofelectrons from said cathode to said luminescent screen.

9. In a color television system, an image reproducing device comprisingin combination a cathode element to develop adjacent thereto anelectronic image of a scanning raster by secondary emission uponbombardment of said cathode element by an electron stream, an electronlens system positioned in said electron stream, a luminescent screen, acontrol electrode positioned between said cathode and said luminescentscreen, means for manitaining said control electrode at a substantiallyconstant potential, said cathode having as a part thereof a plurality ofseparate electrodes, each separate electrode having elements positionedsequentially and extending across substantially all the area of saidcathode, and separate signal channels connected to each group of saidelectrodes of said cathode, and each separate signal channels passing acomponent signal represenative of a component color of a color image.

10. An image reproducing device for converting image signals into imagescomprising in combination a secondary electron emissive electrode, aluminescent screen, an auxiliary electrode and an electron lenspositioned between said secondary electron emissive electrode and saidscreen, said auxiliary electrode arranged to be connected Y' to a pointof substantially constant potential,

means for developing a scanning raster on said secondary electronemissive electrode, and a terminal for applying said signals to saidsecondary emissive electrode.

11. An image reproducing device for converting color image signals intocolor images comprising in combination a secondary electron emissiveelectrode composed of a plurality of groups of selected component colorrepresentative sections, a luminescent screen composed of groups ofselected component color reproducing sections corresponding to thegroups of sections of said secondary electron emissive electrode andWhose sections are in substantial electronic registry with thecorresponding color representative sections of said sectional electrodemeans, an auxiliary electrode and an electron focusing coil positionedbetween said sectional secondary electron emissive electrode and saidluminescent screen, said auxiliary electrode connected to a point offixed potential, means for developing a scanning raster on saidsecondary electron emissive electrode, and means for applying said colorsignals to their corresponding color representative section of saidsectional secondary electron emissive electrode.

GEORGE C. SZIKLAI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,296,908 Crosby Sept. 29, 19422,307,188 Bedford Jan. 5, 1943 2,307,209 George Jan. 5, 1943 2,343,825Wilson Mar. '7, 1944 2,354,263 Hillier July 25, 1944 2,408,050 De RosaSept. 24, 1946 2,446,440 Swedlund Aug. 3, 1948 2,461,515 Bronwell Feb.15, 1949

